Carburetor



Nov. 2, 1948. R. R. sTRl-:BINGER cARBUxE'roR original' me@ July s, 1941 NWN ATTORNEY Patented ov. 2, 1948 CARBURETOR Richard R; strebinger, south Bend, 1nd.,

assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Original application July 5, 1941, Serial No. 401,170. Divided and this applcation'ilune 30, 1944, Serial No. 542,978

4 claims. (Cl. 2in-"23.)

This invention relates to carburetors and more particularly to means for -cgntrolling the throttle valves in multiple stage carburetor systems for internal combustion engines, this application being a division of applicants co-pending application for a carburetor Serial No. 401,170, filed July 5, 1941, now Patent No. 2,376,732 dated May 22, 1945.

Multiple stage carburetor systems for widely variable speed internal combustion engines such as are commonly used in automotive vehicles and the like may comprise either a plurality of separate carburetors or a single carburetor having a plurality of induction passages. In either arrangement there are a plurality of induction pasi sages connectedto a common intake manifold or to complementary manifolds, throttle valves for the respective induction passages, and means for controlling the throttle valves whereby they are opened progressively.

The general purpose of this type of carburetor system is to supply the engine with an economical fuel mixture from a primary source, which may comprise one primary induction passage or a plurality of said passages, throughout the lower speed range which in an automobile engine is used to the greatest extent, and to supply the engine with a supplementary mixture from one or more supplementary or auxiliary induction passages at speeds above said lower speed range, thereby increasing the volume ofthe ymixture delivered to the engine to permit said engine to develop its maximum speed and power. This involves closing or the supplemental passage or passages when the engine is operating under 1cw` speed wide open throttle conditions; in order to furnish the engine with a mixture of combustible proportions under such conditions and permit very low speed operation without misflring orv stalling. The reason the engine will operate at lower speeds without missing when supplied with fuel mixture by one induction passage than when thus supplied by a plurality of passages is that the velocity of the air flowing to the engine through one passage is greater than if the same proved entirely satisfactory in controlling a carburetor system of the multiple stage type so as to accurately meet the fuel mixture requirements of the engine under all operating conditions.

Among the automatic controls for the throttle valves of stages subsequent to the primary stage are various types of suction responsive means which may be connected to one or more of the induction passages. In carburetor systems using such vacuum responsive means for opening the throttle valves of supplemental induction passages, difliculty is sometimes encountered in eiccting the closing of said valves particularly after said valves have been opened to a substantial degree.

It is .therefore an important object of the invention to provide in a multiple stage carburetor system means for controlling the volume and fuelto-air ratio of the fuel mixture according to the requirements of the engine throughout its operating range.

It is a further object of the present invention to provide means for effecting proper closing movement of the supplemental throttle valves of a multiple stage carburetor system employing automatic means for opening said valves, upon deceleratlng movement of the accelerator mechanism.

It is another object of the invention to provide a' device of this character wherein the supplementary throttle valve or valves will be closed by vide a device of this character wherein the throttle valves of supplementary stages are coiftrolled by the position of the throttle valve of a preceding stage.

A further object of the invention is to provide a device of this character wherein the supplementary throttle valve or valves will normally be closed during the starting operation of the engine.

A still further object of the invention is to provide a device of this character wherein the 'supplementary throttle-valve or valves will be positively closed upon closing of the primary throttle valve.

The characteristics and advantages of the invention are further suiciently referred to in connection with the following detailed description of the accompanying drawings which represent certain preferred embodiments. After considering these examples, skilled persons will understand that many variations may be made With- -out departing from the principles disclosed, and I contemplate the employment of any structures,

arrangements or modes of operation that are properly within the scope of the appended claims.

In the drawings:

Figure 1 is a fragmentary elevational view of an internal combustion engine provided with a multiple stage fuel induction system embodying the invention, said system comprising a plurality of independent carburetors shown in vertical section; and

Figure 2 is a vertical section through any integral multiple stage carburetor embodying a modification of the invention.

While the invention is shown and described embodied in a multiple stage carburetor system having one primary andy one supplemental or secondary induction passage it may also be embodied in such a system having a plurality of both primary and supplemental induction passages or a single passage for one stage and a plurality of passages for another stage or stages. It may also be embodied in a system of this character wherein the engine has a dual or multiple type of intake manifold, each part of which has connected therewith corresponding primary and supplemental induction passages.

Throughout 'the drawings, similar reference characters represent similar parts although where such parts are modified in structure and operation, they are given a further diiering reference character.

Referring to Figure 1 reference numeral l0 indicates the engine and I2 the intake manifold thereof having a primary carburetor P and a secondary carburetor S attached thereto. The respective carburetors P and S comprise air horn sections i4 and I5, body sections I6 and l1, and throttle body sections I8 and I9. The induction passages of said carburetors include air entrances 20 and 2|, .small venturis 22 and 23, large venturls 24 and 25, and mixture passages 26 and 21 respectively. Acceleration pumps 2B and 29 and economizer systems 3U and 3| are provided in the respective primary and secondary carburetors, said economizer systems including a valve 32 and vacuum responsive means 34 controlling said valve.

The respective air entrances 20 and 2| are controlled by the usual unbalanced choke valves 3B and 31 on shafts 38 and 39, said valves being controlled by manual or automatic means, not shown, and the mixture passages 2B and 21 are controlled by respective throttle valves 4D and 4| on shafts 42 and 43. The choke Valve 31 may be omitted if desired. The primary and secondary carburetors have idling systems 44 vand 45 respectively and main fuel nozzles 46 and 41 supplied with fuel from fuel chambers 4B and 49 and discharging in the respective small venturis 22 and 23, in the known manner.

The primary carburetor is provided with a fast idle mechanism one type of which is illustrated in the -drawings and which includes a fast idle cam 50 pivoted at 52 and connected with a choke valve lever 54 on shaft 38 by a rod 56. The cam 50 is engageable with a screw 58 in an extension of primary throttle lever 60 secured to one end of the shaft 42, said lever 50 being connected with the usual accelerator pedal or other operating member, not shown, by rod 62.

In Figure 1 the automatic means for controlling the secondary throttle valve 4| includes a casing comprising a pair of cup-like casing members and 12 having a flexible diaphragm 14 marginally clamped therebetween, and thereby providing vacuum chambers 16 and 184 on the respective sides of said diaphragm, said chambers 16 and 18 being connected by respective conduits 'l1 and ,19 with the small venturi 22 of the primary carburetor P and with the intake manifold l2. Conduit 'l1 may, if desired, terminate in an undercut suction tube 11a which extends into said venturi to increase the suction to said conduit 'H relative 'to the suction in the venturi. The diaphragm is suitably connected to one end of a valve actuating rod 8|] having its other end connected by a link 82 with a throttle lever 84 attached to the secondary throttle shaft 43, The actuating rod 80 is slidably received in a boss or bearing 85 integral with casing member'lZ and a sealing ring 88 in a recess 99 prevents leakage of air past said rod B. A suitably calibrated spring 92 in chamber 16 reacts between an adjustable screw 94 and a metal washer 95 secured to the diaphragm 14 and yieldably urges the diaphragm in a direction which normally effects closing of the secondary throttle valve 4|. The spring 92 'is necessary to assure closing of the secondary throttle valve While the engine is being started as the engine should be supplied with fuel .mixture only by the primary carburetor which is a normal one adapted to control the fuel mixture in the usual manner for starting and during the warming up period of engine operation.

The adjustment screw 94 provides means for varying the tension of spring 92 whereby the speed at which the secondary throttle valve begins to open is Varied.

Operation The primary throttle valve 48, being manually controlled, is the valve through which control of the engine speed is effected in accordance with the present invention. In a multiple stage carburetor system itis preferable to maintain the secondary throttle valve closed or substantially closed, as in the idling position, throughout the lower speed range which is customarily used to the greatest extent in an automobile or like vehicle, the primary induction passage supplying the engine with the required fuel mixture throughout said range. The upper limit of said range may be any desired predetermined speed, as for example, fifty miles per hour.

The vacuum device controllingthe secondary throttle valve 4| is actuated by the differential of pressures on opposite sides of the diaphragm 14 and throughout the lower speed range the manifold vacuum, transmitted to chamber 1B through conduit 19 is sufcient with 'the assistance of spring 92-to overcome suction in the small venturi 22 of the primary induction passage, the suction in said small venturi being transmitted to chamber 16 through conduit 11 and increased by the air iiow over the undercut tube 11a. However any other means for varying the pressure in conduit 11 relative to that in the induction passage may be employed.

When the primary throttle valve 40 has been opened beyond the position whereat it will permit enough fuel mixture to be supplied to the engine by the primary induction passage so that the engine speed increases beyond the upper limit of the lower speed range the vacuum in the intake manifold has dropped to a value whereat said vacuum combined with the pressure of spring 92 is insufficient to overcome the vacuum in the small venturi 22 transmitted to chamber 16. As a result the diaphragm will be initially drawn toward the left. as viewed in Figure 1, and the secondary throttle valve 4| will be opened s accordingly. Increased opening of the vprimary throttle valve 40 will effect a corresponding ad ditional opening of the secondary throttle valve 4| due to the further differential of pressures on opposite sides of the diaphragm 14 'resulting in the increased engine speed and increased n uid flow through the primary induction passage anda relative drop in manifold vacuum caused by opening of the secondary throttle valve.l

Under low speed wide open throttle conditions the pressure of spring 92, aidedby the small manifold vacuum then present,` is lsufficient t close the supplementary or secondary throttle valve 4| so that `the engine is supplied with its fuel mixture only by the primary induction paschamber of tiie device is connected with the large venturi |00 of the primary induction passage by means of a conduit which may, if desired. terminate in an undercut suction tube |3| (as shown) extending into said-venturi |03.

The chamber 10 is connected with the mixture. passage V|10 of; said primary passage by a conduit |32; which may terminate as shown in an impact tube |34, posterior to the trailing edge of the primary throttle valve ||0 when said valve is closed. By means of the suction tube |3| and the impact\ tube |30 the pressures in conduits |30 and |32 respectively are varied relative to .the pressure' in the venturi |03 and chamber sage.- Consequently the velocity of theair in l said induction passage is high enough to pick up and sustain sumcient fuel to provide the engine with a mixture of combustible proportions atv This function is effected by the sudden rise in manifold vacuum and the sudden drop in vacuum in the primary induction passage with the closing of the primary throttle valve. The suddenly increased manifold vacuum is transmitted to the chamber 18 while the vacuum in chamber 15 drops to or approximate zero. The diaphragm thereupon moves to the right and, aided by the pressure of spring 92, effects closing of the secondary valve 4|. n

From the` foregoing it is obvious that the means fereclosing the secondary throttle valve includes a controlled force in addition to the spring 92 which is required because the pressure differential between the manifold vacuum and induction passage or Venturi vacuum is at times not very great and it is desirable that the secondary throttle valve be closed, as when'the enr gine is operating at low speed wide open throttle conditions.

A modification 'of the invention is shown in Figure 2, said modification being embodied in an integral multiplestage carburetor hereinafter described although said modification may be embodied in a multiple stage carburetor system having a plurality of independent carburetors.

The integral carburetor shown in Figure 2 is attached to an intake manifold |2a and comprises an air horn section |00, body section |02 and a throttle body section I 04. The primary' and secondary induction passages comprise respectively small venturis |06 'and |01, large venturis |08 and |09 and mixture passages H0 and lil, said induction passages having a common air entrance ||2 controlled by an offset choke valve ||4 mounted on a shaft ||6 and controlled by the usual manual or automatic means.

The mixture passages ||0 and are controlled by the valves ||8 and H9 respectively mounted on shafts |20 and |2l, and a fuel chamber |22 having the usual float mechanism |24, supplies fuel to the main fuel nozzles |26 and |21 and to the idling systems 44 and 45.

Control of the supplementary or secondary throttle valve ||9 is eifected by a vacuum device of the same type as 'that shown in Figure 1. The

||0 and in the present instance a-greater differential of pressureson opposite sides of the diaphragm 'I4 is eflected. Obviously if desired lthe tubes |3| and in may be dispensed with and simple port structures used for one or the other of said tubes or a suction tube may be used instead of the impact tube |34 while an impact tube may be used in place of the suction tube |3|.

The connection between the actuating device for the secondary throttle valve H0 and said valve includes a lever |30 pivoted at |38 and connected at one end with rod 82, the other end of said lever'. |30 being provided with a. slot |40 in which is yreceived a'pin |42 fixed in secondary throttle lever 84 adjacent the end thereof. However any other suitable connection may be used v between the secondary throttle valve and the actuating mechanism therefor.

The operation of the device shown in Figure 2 is as follows:

When the primary throttle valve I I3 is closed or is in the idling position. the entranceor port of tube |34, which is posterior to the leading edge of. said closed valve, is exposed to manifold vacuum which is relatively high and said manifold vacuum is transmitted to chamber 'l0 so that the pressure in said chamber is lower than the pressure in chamber 16 which is connected with the large venturi |03. of the primary induction l vpassage in which the vacuum is very low. Consequently the supplementary throttle valve H9 is held tightly closed by the dierential of pressures on opposite sides of the diaphragm 14, and

by the pressure of spring 02, said. throttle valve il 3 being retained in the closed position throughremain posterior to the valve H8 throughout the range of movement thereof whereby same nor- 'mally controls the speed of the engine up to a predetermined' value, such for example, as fifty miles per hour although the upper limit -of the lower speed range of the engine may be any' other desired value.

As the primary throttle valve H0 is opened the manifold vacuum decreases effecting a correspending decrease in the suction in chamber 18 while the suction in the large venturi |08 of the primary carburetor increases with a corresponding increase of suction in chamber 16. However, untilthe trailing edge of the primary throttle valve passes the entrance of tube |34 the suction in chamber 10 will not be sufficient to overcome the suction in chamber 10 and the force of spring 32 so that the secondary throttle valve will not be opened. However, as soon .as the leading edge of the primary throttle valve passes said entrance to tube |34 the latter is exposed tb a region of relatively low suction and the suction in chamber 1G is sufcient to initially open the supplementary throttle valve H9. Further opening of the primary throttle valve ||8 with the normal increase of engine speed will eifect a further differential of pressures on the opposite sides of the diaphragm which will cause said diaphragm to move in a direction to effect further opening of the secondary throttle valve. Should the engine now be placed under a heavy load while both throttle valve are open the speed Will decrease and upon decrease of the speed to a predetermined low value, spring 92, aided by suction in chamber 18, will overcome the decreased suction in chamber 16, and effect closing of the secondary throttle valve ||9 so that the engine is then supplied with fuel -mixture only by the primary induction passage.

Ii during normal high speed operation of the engine with both valves open, the primary throttle valve l i8 is moved toward the closed position until the trailing edge thereof returns past the tube i3d, the entrance to said tube is posterior to said valve H8 and is exposed to manifold vacuum which is higher than the vacuum then in the large venturi |08. The increased vacuum in chamber 18, together with the force of spring 92, effects quick closing of the secondary throttle valve.

While certain modifications of the invention have been shown and described, it is to be understood that one or more of the various features of one modication may be substituted for corresponding features of another modication, or may be added thereto.

For example, the conduits connecting the vacuum control unit and primary induction passage anterior to the throttle valve thereof may be connected with either large or small venturi adjal cent the throat or at some other suiable part thereof or it may be connected with the induction passage at some other suitable location other than the venturis so long as it is anterior to the throttle valve and is exposed t0 a region wherein pressure within said induction passage will be varied by air flow in the passage.

In the embodiment shown in Figure 2 the tube |34 is located according to the degree of the valve opening desired before the adjacent edge thereof passes the entrance to said tube andl it is to be noted that in any of the embodiments of the invention either an impact tube or a suction tube may be used for any of the connections of the control unit with the induction passages, or the conduits may terminate in simple ports.

It will -be further und-erstood that many other variations can be made fro-m the disclosed embodiments and it is not intended that the scope of the invention shall .be limited to the forms shown and described nor otherwise than by .the terms ofthe appended claims.

I. claim:

l. In a multiple stage carburetor system for an internal combustion engine, a primary and a secondary induction passage, throttle valves coritrolling said passages, a large and a small venturi in the primary induction passage, means for manually controlling the primary throttle valve, suction responsive means for controlling the secondary throttle valve, said last mentioned means having one connection with said small venturi, whereby suction in said venturi tends to open said secondary throttle and said means having anf other connection with the intake manifold whereby suction in said manifold tends to close said secondary throttle Valve.

2. In a multiple stage carburetor system for internal combustion engines: a primary induction passage controlled by a throttle valve; a secondary induction passage controlled by a throttle Valve; manual means for controlling the primary throttle'valve; suction responsive means for operating the secondary throttle valve; a conduit connecting the last mentione-d means with the primary induction passage anterior to the primary .throttle valve and a second conduit vconnecting said means with a source of manifold vacuum, whereby said means tends to open the secondary valve upon an increase in suction anterior to the primary throttle valve and tends to close the secondary valve in accordance with manifol-d vacuum; and means adjacent the induction passage end yof the first mentioned conduit modifying the suction in said conduit relative to that in the induction passage.

3. The invention defined by claim 2 wherein the means for modifying vthe suction in the conduit relative to that in the induction passage is adapted toincrease said suction in said conduit rel-atve .to that in said passage.

4. In a multiple stage carburetor system for an internal combustion engine, primary and secondary induction passages, throttle valves controlling said passages, means in said primary induction passage anterior the primary throttle valve for lcreating suction varying with variations in the flow of air -through the primary induction passage, means for manually actuating the primary throttle valve, and pressure-responsive means for -controlling the secondary throttle valve including a movable wall having an operating connection with said latter valve, one side of said movable wall being subjected to suction created in the primary induction passage and the other side thereof being subjected to manifold vacuum.

RICHARD R. STREBINGER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,519,081 Cozette Dec. 9, 1924 2,193,533 Kishline et al Mar. 12, 1940 2,225,194 Melcher Dec. 1'7, -1940 2,269,930 Ericson et al Jan. 13, 1942 2,315,183 Bicknell et al Mar. 30, 1943 2,327,592 Chisholm Aug. 24, 1943 2,355,716 Ericson et al Aug. 15, 1944 

